Insulating composition for electrical apparatus



May 15, was. 4 1,4552% F. J. GROTEN, JR

INSULATING COMPOSITION FOR ELECTRICAL APPARATUS ol ginal Filed Feb. 26,1920 PUMP Patented May 15, 11923.

entree snares 11,455,200 PATENT @FFHGE.

FRANK J'. GROTEN, JR., OF IVIERIDEN, CONNECTICUT, ASSIGNOR TO THECONNECTICUT TELEPHONE & ELECTRIC CO., INC., OF MERIDEN, CONNECTICUT, ACORPORATION OF CONNECTICUT.

INSULATING COMPOSITION FOR ELECTRICAL APPARATUS.

Original application filed February 26, 1920,'Seria1 11'o. 361,392.Divided and this application filed November 12, 1920.

To all whom it may concern:

Be it known that I, FRANK J. GROTEN, J r., a citizen of the UnitedStates of America, residing at Meriden, New Haven County, Connecticut,have invented a new and useful Insulating Composition for ElectricalApparatus, of which the following is a specification.

The main object of my invention is a compact, durable and eflicientconstruction of coils and condensers for motor ignition Work. Theadjustments of the ignition system are of course dependent upon thecharacteristics of the coil and condenser. It is therefore importantthat all the. devices of a given style shall be uniform in everyparticular so that they will be interchangeable. They must also becapable of quantity production at reasonable cost in order to beavailable for general use. These devices are subjected to varyingelectrical conditlons and to rough usage. As it is practicallyimpossible for the ordinary user or mechanic to inspect or repair such adevice, it should not be subject to deterioration.

To accomplish the best results at a minimum expense, the coils andcondensers are first made up according to suitable specifications. Theprimarycoil may consist of one or more layers of suitably insulated wiresuch as enameled copper. One layer may be wound on a paper tube or on acore and if there is more than one layer, a sheet of insulation such aspaper may be interposed between the layers. The secondary may be made upin the same way usually having a large number of layers of smaller wire.The condenser will usually consist of alternate layers of metal foil andfabric, for instance, two strips of foil wound with paper between.

The primary, secondary and condenser elements are then heated for say4.0 minutes at about 60 C. They are then preferably dried in a vacuum sothat the moisture is sure to be removed without excessive heating. Ihave found a temperature of 60 C. and a vacuum of about 29 inches ofmercury for 90 minutes satisfactory.

The elements are then suddenly immersed in or flooded with a special hotthin liquid compound and subjected to fluid pressure until thoroughlyimpregnated. This may lik Serial No. 423,649.

take say 30 minutes at a pressure of say 25 to 50 lbs. per square inch,and a temperature of say 130 to 135 C. The compound which Ihave foundgives the best results consists of approximately 85% by weight of asynthetic resin and 15% of oil. The resin I prefer to use is known ascumar and consists, I believe, of polymers of paracoum arone, paraindene and polymers of certa n other hydrocarbons obtained from certaincoal tar distillates such as crude naphthalene. The polymerization Iunderstand 1s carried out by the use of sulfuric acid which after thereaction is completed is neutralized with an alkali and the productwashed with water and distilled. The melting point depends upon thetreatment. This substance has the peculiarity that une most gums it canbe heatedconsiderably above its melting point without frothing anddecomposition. Also it is uniform in quality, free from foreign matterand neither acid or alkali. I prefer to use a product having a meltingpoint of about 80 to 100 C. The oil is preferably China wood oil. Themixture must be very liquid well below the'charring temperature of thepaper or other spacing material employed so as to completely anduniformly impregnate the element without damage to the insulation. Themelting point of the mixture is about 60 C. The resin and oil are heatedto a temperature of about 130 C. and mixed so as to be very thin andflow readily when hot. I have found that this compound when handled asabove indicated ensures a device with exceedingly high and uniformdielectric properties which is per manent and reliable in character. Thecoils and condenser for a single device may be assembled beforeimpregnation. This facilitates handling and ensures uniform treatment.

After treatment as above described, the three elements are allowed todrain ofi excess liquid and then with the usual magnetic core and with amagnetic shield if desired, are surrounded by a casing and a fillercompound is poured into the casing and between the elements to moreperfectly insulate the partsand keep out all moisture. This filler ispreferably composed of the same ingredients as the impregnating compoundonly I use a resin having a higher meltirg manner affects theimpregnating compound and at the same time has the property ofregelation at the normal working temperature of the coil so that nodamage is done if it is cracked. It will so to speak be self-healing?The softening point of the filler is about 82 C.

Fig. 1 shows one form of device ready to be impregnated according to mylnvention (full size).

Fig. 2 shows the same elements as Flg. 1, but located in a casing andfilled.

Fig. 3 is a diagrammatic view of apparatus for impregnating according tomy 1nvention.

It will be understood that I have shown but one form of device, and donot consider my invention as limited to any partlcular form of coil orcondenser, or to any particular combination of coils and condenser.

In the particular form shown, 5, 6 and 7 respectively are the primarycoil, secondary coil and condenser. The primary coil is shown as woundon a tube 8, a secondary coil on a tube 9 and the condenser has aninsulating inner layer 10. The core 11 may be of any suitable type and amagnetic shield 12 may be interposed between the secondary coil and thecondenser, The three elements are mounted on a base plate 13 and heldtogether by a rod 14.- and cross piece 15. The layer of insulatingmaterial 16 is shown interposed between the bottom of the shield, thecore and the base plate. Another layer of insulation 17 is showninterposed between the primary and secondary coils and the bottom of theshield 12. As above indicated, the coils and condenser arepreferablyassembled and impregnated as a unit. After the elements havebeen impregnated with the compound as above mentioned, a casing such as18 is placed around the condenser and the filler compound 19 poured inasbefore referred to.

The impregnating process may be conveniently carried out in apparatusindicated diagrammatically in Fig. 3, where 20 indicates a vat or tankadapted to hold a number of the units to be impregnated, and 21indicates a tank for containing the impregnating compound or mixture ofresin and oil. These two tanks may be heated in any suitable way as forinstance by steam jackets. The inner chambers of the tanks are connectedby a pipe 22 having a valve 23. A pump 24 is connected to the innerchamber of tank 20. A condenser may be used between the pump and thetank. In carrying out the process the elements to be treated are placedin the tank 20 and heated for say 40 minutes at a temperature of say 60C. The pump is then startedv and operated so as to produce a vacuum inthe tank 20 of say 29 inches, which is maintained say for an hour and ahalf. Meanwhile the impregnating compound in the tank 21 is heated tosay 130 to 135 C. There is practically no volatilization of the compoundunder these conditions. At the end of the vacuum drying period the valve23 is opened and the impregnating liquid sucked over into the tank 20.The valve 23 is then closed and the pump operated until a pressure ofsay 50 lbs. per square inch is obtained. The coils are left in theimpregnating liquid under this pressure for about a half hour and thetemperature of the liquid maintained at approximately 130 to 135" C. Thevalve 23 is then opened and the impregnating liquid which has not beenabsorbed is forced back into the melting tank 21. The impregnating tank20 is then opened and the coils allowed to drain for a few minutes.After this, reheating to a temperature above boiling water, say 120 C.,will not cause the compound to run out. The coils are then taken out andplaced in the casin s and filled with the filler compound. s theimpregnating compound has a small co-efiicient of expansion the elementcan be taken immediately from the impregnating liquid without danger ofcracking, and without causing the layers to separate as the articlecools.

I have found that a very high and constant dielectric strength isprovided by the use of China Wood oil with the cumar,

and that such a compound ensures a most uniform condition and operationof the ignition element. A drying oil such as boiled linseed oil ma beused instead of China wood oil, but it should be entirely free of waterin, order to produce satisfactory results.

1 It should be understood that I have given the details of only oneparticular product and the particular steps of the preferred processmerely as examples and without intending to limit my claims to the exactproportions, times, temperatures, and pressures given. My invention inthe broader aspect covers the treatment of coils or condensers alone orcombined.

This process of impregnation not only supplements the insulation on thewire and between the layers of the condenser, but seals it uniformlythroughout in case the insulation happens to. be defective. The fillercompound further protects the coils and condenser, and prevents theabsorption of moisture from the air and keeps out surface water, eitherof which would seriously interfere with the operation of the device ifit did not actually ruin it.

The process is claimed in my application meaaoo #361,392, filed February26, 1920, from which this is a division.

I prising a I claim:

1. An impregnating composition having a melting point of approximately60 C. comsynthetic resin formed from the neutral polymers ofpara-coumarone, paraindene and other hydrocarbons obtained frpm a coaltar distillate andmixed with an 01 2. An impregnating compositioncomprising approximately 85% of cumar and approximately 15% of a. dryingoil.

3 n impregnating composition of the character described comprising asynthetic resin formed by polymerization of a coal tar distillate and anoil and having a 'low melting point and a. viscosity of from 11} to 2%min. by the Engler viscosometer at approximately 130 C.

4. An impregnatingcomposition of the character described having amelting point below 70 C. and composed of from 80% to 93% of a neutralresinous polymerization product of the cumar and indene group having amelting point of from 70 to 100 C. and from 20% to 7% of oil.

5. An impregnating composition of the character described with a meltingpoint of approximately 60 C. and containing more than 75% of a neutralresinous polymerization product of the cumar and indene group and adrying oil.

6. An impregnating composition of the character described having amelting point of approximately 60 C. and consisting of a majorproportion of the neutral polymers of para-coumarone, para-indene andother hydrocarbons obtained from a coal tar distillate and a minorproportion of oil which is miscible with it at a. temperature ofapproximately 130 C. without substantial change.

7. An impregnating composition having a melting point below 100 C. andcomposed of a ma or proportionof cumar and a minor proportion of oil.

FRANK J. GROTEN, JR.

